The present invention relates to new and useful structures, components and methods for constructing and operating a manually propelled vehicle such as a wheel chair, including (a) structures, components and methods for automatically locking the wheels of the vehicle when the occupant starts to get out of the vehicle, (b) locking components for locking the wheel of the vehicle against movement, and (c) components of the vehicle that are designed to facilitate assembly of those components into the vehicle.
Wheel chairs used to transport persons that are mobility-impaired have been available for over a century. The first wheel chairs were bulky, heavy and difficult to maneuver. In 1932 the first tubular formed frame wheel chair that was lighter and easier to maneuver was introduced by Harry Jennings. Of necessity, it used folding mechanisms consisting of moveable joints and linkages, etc. to connect the side frames of the chair.
In the applicants' experience, there are currently two commonly used wheel chair designs—the cross brace folding wheel chair and the welded rigid frame wheel chair. Today's disabled population demands lighter, more durable, maneuverable, transportable and utilitarian wheel chairs. Towards that end, in the 1970s a conceptually new wheel chair with a rigid frame was introduced. The wheel chair's side frames are secured to each other by rigid elements (tubes, bars, etc.) by means of welding, which provide a rigid wheel chair without a folding mechanism; such welded rigid frame design may be more expensive due to higher manufacturing costs. However, the absence of a folding mechanism provides the following advantages:                increased strength and durability (fewer moving parts)        increased energy efficiency (folding mechanism absorbed energy needed to propel the chair)        decreased weight (fewer parts)        increased maneuverability        increased stability        increased comfort.        
Examples of wheel chairs that utilize welded joints are disclosed in U.S. Pat. Nos. 4,840390 and 4,981,305 issued to Lockard et al. A sports wheel chair is disclosed in U.S. Pat. No. 4,500,102 issued to Haury et al that includes a one piece, welded tubular frame assembly. Another U.S. Pat. No. 4,721,321 issued to Haury discloses a similar sports wheel chair construction. Another welded wheel chair frame is disclosed in U.S. Pat. No. 4,811,964 issued to Horn for a wheel chair propelled by rowing.
There are also wheel chairs that are modular in design and can change widths of the wheel chair with little difficulty. For example, there is a design that converts from a user-propelled wheel chair to an assistant-propelled wheel chair (see e.g. U.S. Pat. No. 5,294,141). There is also a wheel chair that converts the riding position from the standard seating position to a recumbent position (see e.g. U.S. Pat. No. 5,011,175). In addition, there is a weld-free folding wheel chair that folds in a non-conventional manner but is not modular (U.S. Pat. No. 4,682,783). Another wheel chair design appears to be a weld-free design that allows the wheel chair to adjust to different needs by use of special shaped bars and plates but in the applicants' view is limited to width and depth adjustment (U.S. Pat. No. 5,743,545).
Also, there are several U.S. patents that claim to be modular, allowing for different components to be used to build the chair to the user's needs. Among these is a rigid frame wheel chair (U.S. Pat. No. 5,421,598), but applicants believe this wheel chair does not convert or adapt to the extent of the current invention. A folding frame wheel chair that is moveable between and upper normal sitting position and a lower reclining position that does not utilize welds is disclosed in U.S. Pat. No. 5,011,175 issued to Nicholson, et al. However, such a chair is a folding frame wheel chair. While it includes no welds, it is secured together by means of pivoted members or linkages that render the chair construction less stable and less secure. In applicants' view, the chair has all of the disadvantages of the folding frame wheel chairs.
Also known are numerous clamping element designs for securing two or more tubular members to each other. By way of example only, reference is made to U.S. Pat. No. 4,515,497 issued to Guillemot et. al. for a clamping element for releasable fastening of spatially arranged, or parallel bars, tubes, and similar objects; U.S. Pat. No. 4,039,263 issued to Bassler for a connector arrangement for a minimum of three struts along the spatial axes; U.S. Pat. No. 4,294,561 to Chapman et al for a jointing member for frame systems; U.S. Pat. Nos. 4,597,140 and 4,597,690 issued to Girard for tube clamps; U.S. Pat. No. 3,423,113 issued to Gonsalves et. al. for a connection for tubular members; U.S. Pat. No. 4,784,511 issued to Greene for a connector for tubular frame members; and U.S. Pat. No. 3,216,752 issued to Rifken for coupling means for building frameworks, racks, scaffolds, and the like. In U.S. Pat. No. 4,702,638 issued to Zalesak, inexpensive, molded plastic shells for corners and elbows is disclosed. In U.S. Pat. No. 5,253,888 Friedrich discloses a tubular rigid wheel chair system secured by mating semi-cylindrical shells that can be readily disassembled for transport or repair, but not readily foldable for daily use. In this invention, a series of specially designed clamps had to be utilized that were not universal, and bolts were clearly visible, detracting from the appearance of the wheel chair. In U.S. Pat. No. 6,270,105 Friedrich discloses a wheel chair system that is constructed with distortion-free connectors and that can be configured or adapted to a multitude of end user configurations, still using the tubular construction typical for wheel chairs of this era. Schlangen in U.S. Pat. No. 6,769,705 discloses a rigid non-foldable wheel chair with a system of longitudinal beams to which tubes are attached so that the seat, frame and footrests are releasably connected with supports without welding members, held together instead with expansion devices. In U.S. Pat. No. 6,126,187 Vassilli discloses a modular wheel chair construction of low cost tubes assembled with exposed rivets and screws constructed without welding.
Notwithstanding the fact that numerous clamps have been proposed for securing tubular members to each other, in applicants' experience the wheel chair industry has continued to rely on welded frame construction for rigid wheel chairs. However, the welding/brazing operations have proven to be inconsistent, hazardous, time consuming and expensive. It results in metal fatigue due to crystallization/oxidation, creates a heat-effected zone next to the weld which could lead to a potential safety hazard (i.e., collapse of the chair). It also requires additional operations such as polishing/grinding, electrochemical plating, etc., all of which are hazardous to both workers and to the environment.
All of the above processes would have to be repeated in the case of an accidental failure of the chair (i.e., weld breakage), which would entail a high repair cost. Breakage of welded or brazed joints is the major cause of structural failures in welded wheel chairs.
Almost all manually propelled wheeled vehicles such as wheel chairs have manual wheel locks that prevent the vehicle from rolling when an occupant either attempts to sit in or rise from said vehicle. Because the physically or mentally frail state of many occupants often prevents them from engaging such locks, thereby increasing their risk for injurious falls, many such vehicles also utilize an anti-rollback apparatus. Anti-rollback apparati prevent unintended rearward chair motion when the occupant is attempting to exit or enter said vehicle. Prior constructs to create a self-locking anti-rollback system for self-propelled vehicles such as wheel chairs have suffered from a variety of disadvantages. Some such as U.S. Pat. No. 2,426,451 disclosed by Hammack, and U.S. Pat. No. 4,350,227 by Knoche, rely on pressure on the armrest to lock the chair, which does not take into account when an occupant might get off of the seat by pulling on something like their bed rather than pushing on the armrest. Some disclosures such as U.S. Pat. No. 6,315,085 by Dahlem and U.S. Pat. No. 6,431,572 by Harden require pushing a seat lever out of the occupant's way that engages the brake before they can exit the chair, creating an obstacle for the confused patient. Some disclosures such as Marshall's U.S. Pat. No. 3,529,700, and Kuilk's U.S. Pat. No. 4,852,697 only allow the assistant from behind to lock or unlock the device. Many examples exist of prior attempts to engage the large diameter driving wheel hub as the locking region, requiring intricate and expensive construction or adaptations of existing vehicles such as U.S. Pat. No. 3,897,857 disclosed by Rodaway, U.S. Pat. No. 4,538,825 by Lemarie, U.S. Pat. No. 5,203,433 by Dugas, U.S. Pat. No. 5,799,756 by Roberts, U.S. Pat. No. 6,012,555 by Duran, and U.S. Pat. No. 6,264,007 by Norton. Others require volitional (non-automatic) locking of the hub brake as in U.S. Pat. No. 5,379,866 by Pearce, U.S. Pat. No. 5,984,334 by Dugas, and U.S. Pat. No. 6,341,671 as disclosed by Ebersole. Some automatic locking devices require levers under the seat that are potentially uncomfortable or prone to cause pressure sores as in U.S. Pat. No. 5,894,912 by Dugas, U.S. Pat No. 6,092,824 by Ritchie, and U.S. Pat. No. 7,066,482 by Ford. Other patent disclosures will not allow the wheel chair to collapse and fold when added onto the wheel chair as in U.S. Pat. No. 6,092,824 by Ritchie. Still others focus their attention to the large diameter driving wheel rim or tire itself, but are too complex as is U.S. Pat. No. 4,623,043 by Babilas, or are just for caregiver operation as add-ons to the vehicle as in U.S. Pat. No. 4,852,697 by Kulik. Others such as U.S. Pat. No. 6,352,138 by Duran, or U.S. Pat. No. 6,739,610 by Connors work by leveraging arms into the ground surface when the patient gets up. What is needed is an efficient, simple, reliable, unobtrusive, inexpensive self-locking anti-rollback system for self-propelled vehicles such as wheel chairs that will prevent an incapacitated occupant from experiencing rollaway of their vehicle when exiting or entering same.